Named in honor of US airpower advocate Brig. Gen. William "Billy" Mitchell, the North American B-25 was a true workhorse of World War II. Designed as a medium bomber, it went on to serve as a low altitude strike aircraft, was used for reconnaissance, and anti-submarine duties. B-25s served with the 15th Air Force in Italy and were extensively used in the Pacific, India and China during WWII. After the war, many were used in pilot training and in radar navigator/bombardier training. Many more were given to other countries via military assistance programs. The B-25G and H models carried a 75mm cannon plus machine guns in the nose in place of the station for the navigator/bombardier. It was even used as a personnel transport. 11,433 B-25s (all models) were built in Inglewood, CA and Kansas City, MO.

The last production model, the B-25J, often called a cross between the B-25C and the B-25H. It had a transparent nose, but many of the delivered aircraft were modified to have a solid nose. Most of its 14–18 machine guns were forward-facing for strafing missions.

418 "City of Edmonton" Squadron was one of a total of 164 Mitchells of Mks. I, II, III, and IIIA1 on the strength of the RCAF from 10 July, 1942 to 12 November, 1963. 418 Squadron acquired the "City of Edmonton" appellation on 3 September, 1952 while classified as a Light Bomber Squadron (Auxilliary). HO*891 (see photo below) was one of the most photographed RCAF B-25Ds (formerly USAAF 41-29886) and served from 1944 to 1956 as a photographic Aircraft among other duties.

The B-25 is best remembered in aviation history for its use by Jimmie Doolittle in the raid over Japan in the dark early days of American involvement in World War II. In April 1942, Lt. Col. Doolittle flew the first of 16 specially modified B-25Bs off the deck of the aircraft carrier Hornet. He and his men flew bombing raids over several Japanese cities, including Tokyo.

The raid did relatively little material damage to the Japanese, but the effects on American morale were great. American morale was boosted, while that of the Japanese sank. More important was the reassignment of several Japanese fighter units to the defense of the home islands, rather than to combat in the Southwest Pacific.

For his leadership of the raid, Doolittle was promoted to the rank of Brigadier General and was awarded the Medal of Honor, the United States' highest military award. He went on to command the 12th Air Force in North Africa and, later, the Eighth Air Force in England.

The aircraft on display at Castle Air Museum did not see combat during World War II, but instead served as a test aircraft at what is now Wright-Patterson Air Force Base, Ohio. It was flown into Castle, where General Doolittle was on hand to accept it on behalf of the Museum. It has the group insignia of the 345th Bomb. Group (M), the "Air Apaches" on the tail. The 345th served in New Guinea, the Philippines and ended World War II based on Ie Shima, Okinawa.